In recent years, with evolution of a machining tool, a maximum rotational speed of a spindle has been increasing. In particular, in metal mold machining and micro machining, there is an increasing need for a small-diameter high-precision chuck capable of withstanding precision machining at a super high speed rotation. For realizing such high precision chuck, it is needed to cause a rotational axis of the chuck to agree with an axis of the shank portion of the tool to be gripped thereto.
For instance, PTL 1 discloses a tool chuck including a chuck body having a tubular portion coaxial with a rotational axis, a nut having a female screw in its inner circumference to be screwed with a male screw formed in an outer circumference of the tubular portion to be fitted on this tubular portion, a holder contained in the nut and a collet contained and held within this holder, such that the tool chuck is configured to grip the shank portion of the tool by the inner circumferential face of the collet. With such tool chuck, by screwing the nut into the chuck body, the holder and the collet held thereto can be pushed to the inner side into the tubular portion.